Networking technologies including, for example, computer networks, television networks and telephony networks, continue to facilitate ease of information transfer and convenience to users. In order to provide easier and/or faster information transfer and convenience, telecommunication industry service providers are developing improvements to existing networks. In this regard, for example, improvements are being made to the universal mobile telecommunications system (UNITS) terrestrial radio access network (UTRAN). Further, for example, the evolved-UTRAN (E-UTRAN) is being developed. The E-UTRAN, which is also known as Long Term Evolution (LTE), is aimed at upgrading prior technologies by improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and providing better integration with other open standards.
Recently, efforts have been made to enable the provision of closed subscriber groups (CSGs) to enable restricted access to particular CSG cells for particular groups of subscribers. CSGs may be useful for particular organizations or businesses that wish to define a group of users that may be enabled to freely access a base station, node or access point associated with the CSG, but may have restrictions for enabling access to the cell by individuals outside of the group. CSGs may also be useful in connection with individually established networks within private homes. In this regard, for example, a CSG may typically define a group of users (e.g., subscribers) that are enabled to access a particular CSG cell. As such, individuals that are not members of the group may not be able to access the CSG cell. In some situations, subscribers may be members of multiple CSGs. In practice, a CSG may be associated with one or more cells served by access points, base sites, node-Bs or e-node-Bs that may provide access to subscribers of the CSG.
Current communication standards enable a particular user's mobile terminal to discover possible CSG cells with which the mobile terminal may attempt to communicate using an autonomous search procedure. Mobile terminals may also manually attempt to communicate with CSG cells. The mobile terminal is authorized to access CSG cells for which the CSG identity is within the mobile terminal's CSG “whitelist”, that is, a list provided by non-access stratum containing all of the CSG identities of the CSGs to which the user of the mobile terminal belongs.
In operation, a mobile terminal may acquire the routing parameters and CSG ID of a CSG cell by reading system information blocks for the respective cell. Specifically, for a UTRAN CSG cell, the MIB and SIB1 may be acquired, while for an E-UIRAN CSG cell, the MIB and the SIB3 may be acquired. These routing parameters may include, for example, a tracking area identifier (TAI), a cell global identifier (CGI), a radio network controller identifier (RNC-ID) and/or the like. Based upon measurements of the signal strength or signal quality and other signalling parameters of the cells that are in communication with the mobile terminal, the mobile terminal may issue measurement reports to the macrocell so that the macrocell may make informed decisions as to the CSG cell to support subsequent communications with the mobile terminal.
CSG cells may be deployed in an uncoordinated manner within a macrocell with two or more CSG cells operating on the same frequency and sharing the same physical layer identity, such as a physical layer cell ID (PCI) in an E-UTRAN cell or a primary scrambling code (PSC) in a UTRAN cell. Thus, the macrocell and the mobile station may not be able to uniquely identify a CSG cell based solely on its physical layer identity and the frequency on which the CSG cell operates, thereby leading to PSC or PCI confusion. As such, the cell global identifier (CGI) may be utilized to uniquely identify the CSG cell, not only within the macrocell, but also more globally within the network. Thus, in making measurement reports to the macrocell, mobile terminals may identify the CSG cells by their CGI and, in some instances, with additional identifiers. Similarly, a macrocell could include the CGI of a CSG cell in a cell change order so as to uniquely identify the target cell to which the mobile terminal should transition. However, the CGI is relatively sizable, such as 28, bits, and therefore consumes an undesirably large portion of the measurement reports, thereby disadvantageously limiting the quantity of other information that may be transmitted in the measurement reports. Similarly, the CGI undesirably increases the size of a cell change order, thereby requiring that additional data be transferred between the macrocell and a CSG cell.
As such, it would be desirable to provide an improved technique for identifying CSG cells in a more efficient manner such that the identification of CSG cells consumes a smaller percentage of the signalling between a mobile terminal and a macrocell.